Aftermath of a Leaking Drain. Causes so much damage!

While back we had to come over and figure out why the bathroom was having water/ mold issue, we traced it to a leaking copper drain in the upstairs unit. replace drain and repaired the bathroom. Months later we started getting issues about it happening in the kitchen. Here is a video on our issues and fast recording of me replacing it. At first I though it wasn't part of the same issue but couldn't find any other reason for it. The damage had also spread into the kitchen walls.